Brominated aromatic compounds possess a wide spectrum of industrial applications, such as in the pharmaceutical industry, as fire retardants, as herbicides, biocides and as various intermediates in organic synthesis.
Most aromatic bromination processes in current use are carried out in the presence of various Lewis acids serving as catalyst. Those known processes suffer from many disadvantages, such as the requirement of large amounts of catalyst, the requirement for anhydrous conditions and the substantial amounts of sewage discharged, which often rise serious disposal problems. Furthermore, bromination of aromatic compounds, in particular non-activated aromatic compounds, is a time consuming process, and the yields obtained by the known processes are relatively low.
Another known bromination route consists of the diazotation of the corresponding anilines, followed by thermal decomposition in the presence of bromide ion. Such route suffers from the disadvantages that it requires a suitable aniline derivative which is not always commercially available and that the required reaction periods are generally long.
A recently published research by S. Rozen and M. Brand in J. Chem. Soc. Chen. Comm. (1987) pages 752 and 753 discloses a process for the bromination of aromatic compounds utilizing bromine fluoride as the brominating agent. The bromine fluoride is prepared in situ by bubbling fluorine through a solution of bromine suspended in an organic solvent such as trichlorofluoromethane, at a low temperature ranging between -45.degree. C. to -78.degree. C. The major disadvantages of the above process rises from the extensive cooling and the large quantities of solvent required for preparing the brominating reagent. The large quantities of solvent are required, since concentrated solutions of bromine fluoride tend to decompose. As a result, only small amounts of the aromatic compounds can be brominated, or alternatively exceptionally sizable reactors are required.